There are a variety of adhesives for composites such as particle boards, fiber boards, and textile composites. Generally these adhesives are made from urea-formaldehyde resins, melamine-urea-formaldehyde resins, phenol-formaldehyde resins, and the like. In order to impart sufficient water-resistant properties to the constructions made with these resins, attempts have been made to combine a wax emulsion sizing agent with the resin. However, it has been very problematic to obtain a stable blend of resin and wax emulsion. Wax solids may not remain homogeneously suspended in mixtures with water-borne resins, particularly during transport, transfer, and use. Thus, the resin-wax blend needs to be used immediately or else separation occurs resulting in non-uniformity in the water-repellency and bond quality imparted to the composite by the (combined, mixed or blended) resin and wax emulsion. Also, the amount of wax that is incorporated into the billet is very difficult to control or determine. Further, since wood shris and swells as its moisture content varies, if the composite is not properly treated with a sizing agent and resin, the composite will have poor dimensional stability on exposure to moisture.
Often the wax emulsion is combined with the resin at the time of use. Although it would appear to be more convenient to provide the user with a ready-to-use adhesive that requires no mixing prior to application, however the end user may want the flexibility of combining the resin and wax in different proportions at his site. Thus, there have been attempts to modify the wax to make it more compatible with the resin. U.S. Pat. No. 4,407,999, for example, describes a method of oxidizing the wax used to make an emulsion which could be blended with adhesives. Another method that leads to improved resin/wax compatibility is combining a wax emulsion with a pH that closely matches that of the resin and adding this emulsion to the rein while the resin is hot.
These prior art methods require changes in the manufacturing procedures of the wax or wax emulsion and/or special handling of the wax emulsion and additional manufacturing steps to achieve resin/wax compatibility. It is desirable to provide a resin/wax combination that does not require special treatment of the wax prior to combination with the resin. This would allow the end user maximum flexibility when combining the resin and wax emulsion.